In the field of graphic arts, in order to optimize the reproduction of a continuous tone image or line image from a halftone image, an image formation system which exhibits an ultrahigh contrast (particularly .gamma. of 10 or more) is required.
An image formation system which comprises development with a processing solution having an excellent storage stability to obtain a photographic image with an ultrahigh contrast has been desired. As such an image formation system, a process has been proposed which comprises processing a surface latent image type silver halide photographic material comprising a specific acyl hydrazine compound with a developer having a pH value of 11.0 to 12.3 and containing a sulfurous acid preservative in an amount 0.15 mol/l or more to form an ultrahigh contrast with .gamma. of more than 10 as disclosed in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606 and 4,311,781. While the conventional ultrahigh contrast image formation processes can be carried out only with silver bromochloride having a high silver chloride content, this new image formation process is characterized in that silver bromoiodide and silver bromochloroiodide can be used as well. While the conventional lith developers can contain only an extremely small amount of sulfurous acid preservative, this new developer can contain a large amount of sulfurous acid preservative and thus provide a relatively high storage stability.
However, a developer having a pH value of 11 or more is susceptible to air oxidation and thus is too unstable for prolonged storage or use.
In an attempt to form a high contrast image, an approach has been proposed to develop a silver halide photographic material containing a hydrazine compound with a developer having a lower pH value.
JP-A-1-179939 and JP-A-1-179940 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") disclose a processing method which comprises processing of a photographic material containing a nucleating agent having a group to be adsorbed to silver halide grains with a developer having a pH value of 11.0 or less in the presence of a nucleation development accelerator containing a group to be adsorbed to silver halide grains. However, the emulsion used in these inventions comprises silver bromide or silver bromoiodide, which is susceptible to great fluctuation in photographic properties with fluctuations in the progress of development or the composition of the processing solution and thus leaves much to be desired in terms of stability.
U.S. Pat. Nos. 4,998,604, 4,994,365, and 4,975,354 disclose hydrazine compounds having repeating units of ethylene oxide and hydrazine compounds having pyridinium groups. However, the description of examples shows that these inventions leave much to be desired in contrast development and thus can hardly provide a high contrast and a required Dmax under practical development conditions.
Further, a nucleatable hard contrast photographic material comprising a hydrazine derivative is susceptible to great fluctuation in photographic properties with changes in the pH value of the developer. The pH value of the developer shows great fluctuation with changes in the conditions. In other words, the pH value shows a rise due to air oxidation of the developer or the concentration of the developer by the evaporation loss of water or a drop due to the absorption of carbon dioxide in the air. Accordingly, an approach for a smaller dependence of photographic properties on the pH value of the developer has been attempted.
Examples of the use of chemically sensitized silver bromochloride in a hydrazine system are disclosed in JP-A-53-20921, JP-A-60-83028, JP-A-60-140399, JP-A-63-46437, JP-A-63-103230, JP-A-3-294844, JP-A-3-294845, and JP-A-4-174424. On the other hand, examples of the combined use of a hdyrazine and a silver halide emulsion containing a heavy metal complex such as rhodium and iridium are disclosed in JP-A-60-83028, JP-A-61-47942, JP-A-61-47943, JP-A-61-29837, JP-A-62-201233, JP-A-62-235947, and JP-A-63-103232.
Many examples of cyanine dyes having an anionic charge contained in a hydrazine system have been disclosed, including an alkaline salt of 5,5'-dichloro-9-ethyl-3,3'-bis(3-sulfopropyl)oxacarbocyanine. These examples are disclosed in JP-A-61-29837, JP-A-62-235947, JP-A-62-280733, JP-A-62-280734, JP-A-2-40, JP-A-2-124560, JP-A-2-262653, and JP-A-3-63641.
However, the use of chemically sensitized silver bromochloride is disadvantageous in that a photographic material comprising such an emulsion coated thereon shows a rise in sensitivity after prolonged storage and hence a worsened black pepper phenomenon.
The black pepper phenomenon comprises black spots made of minute developed silver grains formed on a portion which would be unexposed and would not form any image. This phenomenon causes a trouble in photomechanical processes.
U.S. Pat. Nos. 4,998,604, 4,994,365, and 4,975,354 disclose hydrazine compounds having repeating units of ethylene oxide and hydrazine compounds having pyridinium groups. However, as is evident from examples, these inventions leave much to be desired in contrast development and thus can hardly provide a high contrast and a required Dmax under practical development conditions.
On the other hand, the use of a hydrazine compound which is active enough to provide a high contrast and a required Dmax is disadvantageous in that it gives a rise in sensitivity after a prolonged storage and hence a worsened black pepper phenomenon.
The incorporation of a mercaptoazole represented by general formula (7) in a silver halide photographic material containing hydrazine is exemplified in JP-A-56-67843, JP-A-58-191245, JP-A-60-83028, JP-A-61-47944, and JP-A-63-103232.
The incorporation of a triazine compound represented by general formula (8) in a silver halide photographic material containing hydrazine is exemplified in JP-A-4-365032.
The incorporation of a dihydroxybenzene represented by general formula (9) in a silver halide photographic material containing hydrazine is exemplified in JP-A-61-233734 and JP-A-1-55549.
The incorporation of a thiosulfonic acid represented by general formula (10), (11) or (12) in a silver halide photographic material containing hydrazine is exemplified in JP-A-1-237538.